Tip: Temporarily Converting a WPF Library Project to an Executable (WinExe) Project
Developers that pattern after Prism can find themselves generating “modules” as Class Library projects. In Visual Studio 2012 (or earlier), when the Application > Output type: is Class Library it will not be possible to add a new WindowXAML file to the project. The New Item… dialog (with the WPF node selected) will only contain the User Control option.
To work around this situation, select Edit Project File and change OutputType to WinExe (from Library). You may also need to add a <ProjectTypeGuids> element shown below:
Surely this issue is fixed in Visual Studio 2013? Right?